divert(-1)
#
# Copyright (c) 1998-2000 Sendmail, Inc. and its suppliers.
# All rights reserved.
# Copyright (c) 1983 Eric P. Allman. All rights reserved.
# Copyright (c) 1988, 1993
# The Regents of the University of California. All rights reserved.
#
# By using this file, you agree to the terms and conditions set
# forth in the LICENSE file which can be found at the top level of
# the sendmail distribution.
#
#
ifelse(defn(`_ARG_'), `', `errprint(`Feature "nullclient" requires argument')',
`define(`_NULL_CLIENT_', _ARG_)')
#
# This is used only for relaying mail from a client to a hub when
# that client does absolutely nothing else -- i.e., it is a "null
# mailer". In this sense, it acts like the "R" option in Sun
# sendmail.
#
divert(0)
VERSIONID(`$Id: nullclient.m4,v 8.21.16.3 2000/09/17 17:04:22 gshapiro Exp $')
divert(-1)
undefine(`ALIAS_FILE')
define(`MAIL_HUB', _NULL_CLIENT_)
define(`SMART_HOST', _NULL_CLIENT_)define(`confFORWARD_PATH', `')ifdef(`confFROM_HEADER',, `define(`confFROM_HEADER', `<$g>')')define(`_DEF_LOCAL_MAILER_FLAGS', `lsDFM5q')MASQUERADE_AS(_NULL_CLIENT_)FEATURE(`allmasquerade')FEATURE(`masquerade_envelope')MAILER(`local')MAILER(`smtp')

I replace FEATURE(`nullclient',`host.example.com') with the above lines in bold from nullclient.m4.